The present invention relates to thermostats for controlling a temperature in a storage room of refrigerators.
Thermostats are widely used to control a temperature in a storage room of refrigerators. Such a thermostat is disclosed in Japanese Utility Model Publication No. S56-2546. A conventional thermostat is described hereinafter with reference to FIGS. 6 and 7. FIG. 6 shows a front view of the conventional thermostat, and FIG. 7 shows a lateral view of the same thermostat. In FIGS. 6 and 7, housing 101 is made from metal plate undergone press working that forms the metal plate into one-piece housing. Housing 101 is formed of upper face 102, two long side-faces 103 and one short side-face 104.
Switch section 105 is placed such that it faces short side-face 104 of housing 101. Bottom plate 106 faces upper face 102. On upper face 102, adjusting shaft 107, cam 107a formed at the root of shaft 107, and adjusting plate 108 displaced by cam 107a are provided.
Switch section 105 has a switch mechanism (not shown) inside housing 101, and coupling terminals 105a, 105b protruding outward from housing 101. Beneath bottom plate 106 bellows 109 is prepared, and it communicates with the inside of housing 101, so that displacement of bellows 109 activates the switch mechanism of switch section 105. Bellows 109 is filled with gas that is expanded or compressed in response to an atmospheric temperature.
Tube 110 extends from bellows 109 by a given length and communicates with the inside of bellows 109, so that tube 110 is also filled with the gas.
The gas in tube 110 is expanded or compressed in response to the atmospheric temperature. An expansion prolongs bellows 109, thereby operating the switch mechanism to close a circuit. A compression, on the contrary, shortens bellow 109, thereby releasing the switch mechanism from the operation and opens the circuit.
Rotating shaft 107 by a given angle causes cam 107a to rotate by a given angle, so that adjusting plate 108 rotates along cam 107a to produce displacement. This displacement of adjusting plate 108 strengthens or weakens force of operating the switch mechanism. A balance between this operating force and working force of bellows 109 at expansion or compression can set a temperature at which the circuit opens or closes. Long side-face 103 has supporting hole 103a for supporting fulcrum 108a on which adjusting plate 108 rotates, and fulcrum 108a exposes itself outward.
Adjusting screw 111 is prepared for fine adjustment of the temperature set by the rotational position of adjusting shaft 107. A user can rotate screw 111 with a driver via through-hole 104a punched on short side-face 104.
However, since the foregoing conventional thermostat has fulcrum 108a, related to adjusting plate 108, exposed from supporting hole 103a, a user is liable to touch fulcrum 108a with a finger when the user holds housing 101 in the hand, so that the set temperature tends to change.
Further, the foregoing conventional thermostat has adjusting screw 111 at an upper section of housing 101, and switch section 105 is placed at a lower section of housing 101, so that coupling terminals 105a, 105b protrude downward, which makes housing 101 unstable. In order to make housing stable, long side-face 103 or short side-face 104 should face downward, then a user looks at adjusting screw 111 laterally, which makes an adjustment difficult.
The present invention addresses the problems discussed above and aims to provide a thermostat that comprises the following element:
a housing;
a switch mechanism having contacts and accommodated in an outer shell;
a temperature sensing section which converts a volume change of gas being expanded or compressed in response to an atmospheric temperature into force for operating the switch mechanism;
a lever for opening or closing the contact by rotating itself on a first fulcrum with the force supplied from the temperature sensing section;
an adjusting plate engaged with the lever and rotating itself on a second fulcrum for increasing or decreasing the force necessary for rotating the lever; and
a cam shaft having a cam that rotates the adjusting plate.
The housing is placed outside a supporting wall that supports the first and the second fulcrums, and includes a wall that covers both the fulcrums.